Microbial inactivation kinetics of Salmonella spp in dairy powders

Obj 1. Investigate the moisture sorption isotherm of dairy powder at different temperatures Obj 2. Evaluate the effect of water activity on microbial inactivation kinetics of Salmonella in dairy powders Obj 3. Assess the effect of product matrix (fat content) on microbial inactivation kinetics Abstract: Salmonella contamination of dairy powders has resulted in several foodborne outbreaks. Spray drying does not guarantee the food safety of dairy powders, so a thermal processing kill-step is necessary to ensure the safety of these commodities. At low water activity, Salmonella is highly resistant to thermal processing and its resistance varies dramatically with moisture content and temperature. Therefore, it is necessary to investigate the fundamental microbial inactivation kinetics of Salmonella for developing thermal pasteurization protocols for dairy powders. A vapor sorption analyzer will be used to determine the isotherm describing relationship between moisture content and water activity at various temperatures. The custom-made thermal death sandwich system will be used for accurate determination of microbial inactivation kinetics parameters of dairy powders at different water activities and fat content (whole milk powder vs non-fat dried milk powder). Data produced in this project will be critical for developing both traditional thermal pasteurization systems and novel radiofrequency processing systems to enhance safety of dairy powders.